Many industries, including the locomotive industry, are exploring and developing alternative fuels and technologies. For instance, some engines have been developed that depend entirely on natural gas, while other engines have been developed that are hybrid engines, which may include bi-fuel engines that change operating mode enough to be considered hybrid, having dual fuel capabilities, e.g., natural gas and diesel fuels. Compressed natural gas and LNG have both been explored as alternative fuels. Compressed natural gas has a low energy density and has high pressure storage requirements, which makes it a costly and less efficient alternative. LNG, on the other hand, has an energy density much higher than compressed natural gas and can be stored at much lower pressures than compressed natural gas. As such, the locomotive industry has been looking to LNG as a viable fuel alternative.
Special tender cars are used with locomotives that have cryogenic tanks for storing and transporting the LNG at low pressure and temperatures of between about −280° F. and −180° F. The tanks are thermally insulated to reduce heat transfer into the LNG from the environment. Cryogenic pumps and vaporizers, and additional equipment, are used to warm the LNG to convert the LNG into a gaseous state and deliver the gas to the engine at an appropriate pressure.
Some LNG fuel systems, such as those used for fueling locomotives, have external, or non-submerged, cryogenic pumps. External cryogenic pumps need to go through a period of cool down before they are ready for rated operation. During the cool down period, LNG is gradually introduced to the pump, where it flashes to natural gas vapor, cooling down the pump in the process. The process of cooling down the pump creates two problems: first, the cool down process takes a long time, such as, for example, around 30 minutes; and secondly, the cool down process creates a large amount of LNG vapor that must be stored or vented. Since natural gas is a potent greenhouse gas, venting is not environmentally sound practice.
WO 2015/095956 to Rosa et al. (hereinafter “Rosa”) discloses a control system for managing a supply of gaseous fuel on a tender car. In particular, the control system controls the transitioning between a plurality of states, or operational modes, of the tender car. For example, the supply of gaseous fuel on a tender car requires the coordination of a variety of operational modes, such as delivering, refueling, draining, capturing and storing gaseous fuel. However, the Rosa reference does not discuss or address the issues associated with the creation of LNG vapor.
As should be appreciated, there is a continuing need to provide improved systems and methods for efficiently utilizing alternative fuels.